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Chapter 6Optimisation of CRA using adaptive CSAs pFor Internet traffic at 64 kbps per station, the highest system throughput was achievedwith the Variable-CSA and the lowest access delay with the Forced-CSA. For theVariable-CSA two configurations were used. The maximum system throughput ofapproximately 51% at 52% of the channel capacity (generated by 25 stations) was foundby allocating at least 3 CSs per signalling frame. For this traffic type, a slight increase inthe average number of CSs needed per request (with 2.871 CSs) was registered, whichresulted in a small reduction in system performance of 0.2% in comparison with Internettraffic at 32 kbps.For a better appreciation of the performance impact when using enhanced CSAs, amixed traffic situation will be carefully analysed. For this traffic type (comprised of 32kbps Internet and 9.7 kbps VoIP traffic), the maximum theoretical bound for the systemthroughput can now be estimated by taking the mean packet size transmitted (measuredin bytes and in slots), as indicated in Equation 6.4.PkPbIP⋅ PkIP+ PbVoIP⋅ PkVoIPSmax ==(6.4)Pk + eCSs Pb ⋅ Pk + Pb ⋅ Pk eCSsslots IP slots_IP VoIP slots_VoIP+where Pk IP (=368.1) and Pk slots_IP (8.3) are the average Internet packet sizes measured inbytes and data slots respectively. Similarly, Pk VoIP (=146) and Pk slots_VoIP (=4) are theVoIP packet sizes measured in bytes and data slots respectively. Finally, Pb IP and Pb VoIPare the probability that an IP or VoIP packet will be generated, respectively. Equations6.5 and 6.6 give these probabilities.PbPbDrIPIP= (6.5)PkIPDrIP+ ⋅ DrVoIPPkVoIPDrVoIPVoIP= (6.6)PkVoIPDrVoIP+ ⋅ DrIPPkIPwhere Dr IP (= 32 kbps) and Dr VoIP (= 9.7 kbps) are the mean data rates of Internet andVoIP traffic generated per station, respectively. Therefore, the maximum theoreticalsystem throughput that can be yielded for mixed traffic is 46.4% of the channelcapacity.6-13
Chapter 6Optimisation of CRA using adaptive CSAs pWith reference to Figure 6.7, we can appreciate that with an offered load over 46% ofthe channel capacity (produced by 34 stations), the highest system throughput wasranged from ≈ 45.5 to 46% with the configurations Forced-CSA(FSs-2, CSs-2) andForced-CSA(FSs-2, CSs-3). The maximum deviation between simulation and theoreticalresults was under 1% of the cc with an offered load above 46%.46.546.045.5System Throughput (%)45.044.544.043.543.042.542.041.5Simple-CSA(CSs-3)Simple-CSA(CSs-5)Forced-CSA(FSs-2,CSs-2)Forced-CSA(FSs-2,CSs-3)Variable-CSA(CSs-2)Variable-CSA(CSs-3)3 Mbps Upstream32 Kbps kbps IP IP &9.7 Kbps kbps VoIPBackoff CRA31 32 33 34 35 36 37 38 39 40umber of Active StationsFigure 6.7 – System throughput vs. No. of active stations.Exponential backoff algorithm with varying CSA applied.6-14
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I would like to thank all the peopl
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CHAPTER 6: OPTIMISATIO OF CRA ALGOR
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FIGURE 5.17 - SYSTEM THROUGHPUT VS.
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LIST OF TABLESTABLE 2.1 - NEXT GENE
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Chapter 1Introduction pBecause of h
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Chapter 1Introduction pA first step
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Chapter 1Introduction passumption i
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Chapter 1Introduction ppolynomial b
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Chapter 1Introduction pIn general,
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Chapter 1Introduction pminislots to
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Chapter 1Introduction pThe authors
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Chapter 1Introduction prate access
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Chapter 1Introduction p1.4 Overview
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Chapter 2OVERVIEW OF CURRENT CATVNE
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Chapter 2Overview of current CATV n
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Chapter 3THE DVB/DAVIC PROTOCOL3.1
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Chapter 3The DVB/DAVIC protocol pEu
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Chapter 3The DVB/DAVIC protocol pMA
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Chapter 3The DVB/DAVIC protocol pTh
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Chapter 3The DVB/DAVIC protocol p3.
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Chapter 4Simulation and analytical
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Chapter 7Performance optimisation f
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Chapter 7Performance optimisation f
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Chapter 8Final conclusions p8.2 Gen
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Chapter 8Final conclusions pWe have
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Chapter 8Final conclusions pperform
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Chapter 8Final conclusions pslots i
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Chapter 8Final conclusions pfocused
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Chapter 8Final conclusions preserva
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Chapter 8Final conclusions pbandwid
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Chapter 8Final conclusions pThe opt
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Chapter 8Final conclusions p8.4 Fut
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Chapter 8Final conclusions pApplica
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Chapter 8Final conclusions pTCIS st
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Referencesp[17] I. Cidon, and M. Si
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Referencesp[50] N. F. Huang, C. A.
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Referencesp[85] V. Rangel, R. Edwar
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Referencesp[112] K. Sriram, “Meth
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APPEDIX A: GLOSSARYAALABRADSLATMBCB
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Appendix AGlossary pkbpsLANLLCMACMA
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Appendix AGlossary pUSBUWVDSLVoDVoI
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Appendix BProtocol stack and packet
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Appendix BProtocol stack and packet
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APPENDIX C: D VERIFICATION TEST FOR
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Appendix D Verification test p209 2
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Appendix EResults for a 6 Mbps upst
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Appendix FGuide to CD-ROM p IEEE802
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